CN107709620B - Method and apparatus for manufacturing cold-rolled steel strip - Google Patents
Method and apparatus for manufacturing cold-rolled steel strip Download PDFInfo
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- CN107709620B CN107709620B CN201680039032.XA CN201680039032A CN107709620B CN 107709620 B CN107709620 B CN 107709620B CN 201680039032 A CN201680039032 A CN 201680039032A CN 107709620 B CN107709620 B CN 107709620B
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- 239000010960 cold rolled steel Substances 0.000 title claims abstract description 85
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title abstract description 20
- 239000002253 acid Substances 0.000 claims abstract description 327
- 238000005554 pickling Methods 0.000 claims abstract description 95
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 69
- 239000010959 steel Substances 0.000 claims abstract description 69
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 238000005097 cold rolling Methods 0.000 claims abstract description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 117
- 239000007788 liquid Substances 0.000 claims description 88
- 229910017604 nitric acid Inorganic materials 0.000 claims description 41
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 40
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 21
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 21
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 21
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 20
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- 238000006243 chemical reaction Methods 0.000 abstract description 42
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- 238000005260 corrosion Methods 0.000 abstract description 23
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- 230000008569 process Effects 0.000 abstract description 6
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- 238000010924 continuous production Methods 0.000 abstract 1
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- 239000013585 weight reducing agent Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
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- 230000005540 biological transmission Effects 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 239000013527 degreasing agent Substances 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
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- 238000002003 electron diffraction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 229960002050 hydrofluoric acid Drugs 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
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- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- NICDRCVJGXLKSF-UHFFFAOYSA-N nitric acid;trihydrochloride Chemical compound Cl.Cl.Cl.O[N+]([O-])=O NICDRCVJGXLKSF-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Images
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
- C23G1/085—Iron or steel solutions containing HNO3
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G3/00—Apparatus for cleaning or pickling metallic material
- C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
- C23G3/021—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously by dipping
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G3/00—Apparatus for cleaning or pickling metallic material
- C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
- C23G3/027—Associated apparatus, e.g. for pretreating or after-treating
- C23G3/028—Associated apparatus, e.g. for pretreating or after-treating for thermal or mechanical pretreatment
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G3/00—Apparatus for cleaning or pickling metallic material
- C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
- C23G3/027—Associated apparatus, e.g. for pretreating or after-treating
- C23G3/029—Associated apparatus, e.g. for pretreating or after-treating for removing the pickling fluid from the objects
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
Provided is a method for producing a cold-rolled steel strip, which enables the continuous production of a cold-rolled steel strip having excellent chemical conversion treatability, excellent post-coating corrosion resistance in a severe corrosive environment, and excellent surface appearance quality, stably over a long period of time. The method for producing a cold-rolled steel strip according to the present invention is characterized by comprising a step of continuously immersing a continuously annealed steel strip after cold rolling in a mixed acid solution containing an oxidizing first acid and a non-oxidizing second acid to thereby perform pickling; and thereafter, continuously immersing the steel strip in an acid solution containing a non-oxidizing third acid to perform a re-pickling process, wherein the concentration of the first acid in the acid mixture is changed to be lower and the concentration of the second acid is changed to be higher as the concentration of iron ions in the acid mixture increases.
Description
Technical Field
The present invention relates to a method and an apparatus for manufacturing a cold-rolled steel strip.
Background
In recent years, from the viewpoint of global environmental conservation, improvement of fuel efficiency of automobiles is strongly demanded. In addition, from the viewpoint of ensuring safety of passengers at the time of collision, there is also a strong demand for higher strength of automobile bodies. In order to meet these requirements, it is actively promoted to increase the strength and thickness (reduce the weight) of cold-rolled steel sheets as a raw material of automobile parts, thereby achieving both weight reduction and strength increase of automobile bodies. However, since many automobile parts are manufactured by forming cold-rolled steel sheets, cold-rolled steel sheets used as raw materials thereof are required to have not only high strength but also excellent formability.
Various methods are used to increase the strength of cold-rolled steel sheets, and a solid solution strengthening method using Si addition is an effective means for increasing the strength without significantly losing formability. However, it is known that when a large amount of Si, particularly 0.5 mass% or more of Si is added to a cold-rolled steel sheet, a large amount of SiO is formed on the surface of the steel sheet during slab heating, hot rolling, or annealing after cold rolling2Si-containing oxides such as Si-Mn based composite oxides. Since the Si-containing oxide significantly reduces the chemical conversion treatability, a high-strength cold-rolled steel sheet containing a large amount of Si is deteriorated in the chemical conversion treatability. Further, the following problems are present in the case of a high-strength cold-rolled steel sheet containing a large amount of Si: after the electrodeposition coating, when the steel sheet is exposed to a severe corrosion environment such as a hot-salt water immersion test or a combined cycle corrosion test in which wet-dry is repeated, the steel sheet is more likely to suffer from peeling of the coating film than a normal cold-rolled steel sheet, and the corrosion resistance after the coating is deteriorated. Therefore, it is difficult to use a high-strength cold-rolled steel sheet containing a large amount of Si for automotive body applications requiring coating.
As a technique for solving the above problems, there are patent documents 1 and 2. Patent documents 1 and 2 describe a method for producing a cold-rolled steel sheet including the steps of: a step of pickling the continuously annealed steel sheet by continuously immersing the steel sheet in a mixed acid of nitric acid and hydrochloric acid or nitric acid and hydrofluoric acid after cold rolling; and thereafter, continuously immersing the steel sheet in a non-oxidizing acid such as hydrochloric acid or sulfuric acid to re-pickle the steel sheet. This method removes Si-containing oxides on the surface of the steel sheet in the pickling step and removes iron-based oxides generated in the pickling step in the re-pickling step, thereby making it possible to produce a cold-rolled steel sheet having excellent chemical conversion treatability and post-coating corrosion resistance in a severe corrosive environment.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2012 and 132092
Patent document 2: japanese laid-open patent publication No. 2012 and 188693
Disclosure of Invention
Problems to be solved by the invention
However, the inventors of the present application have studied and found that, when the cold-rolled steel strip is continuously passed through a manufacturing facility capable of performing the above-described two-stage pickling and the above-described two-stage pickling is continuously performed on the cold-rolled steel strip, the surface appearance quality of the cold-rolled steel strip manufactured at that time is gradually deteriorated with the passage of time. Specifically, it was found that the surface of the cold-rolled steel strip immediately after the pickling step in the first stage was discolored to reddish brown due to some deposits as time passed, and the discoloration was not removed in the re-pickling step in the second stage. Among such cold-rolled steel strips having deteriorated surface appearance quality, there are those having deteriorated chemical conversion treatability and corrosion resistance after coating in a severe corrosive environment.
In view of the above problems, an object of the present invention is to provide a method and an apparatus for producing a cold-rolled steel strip, which can continuously produce a cold-rolled steel strip excellent in any of chemical conversion treatability, post-coating corrosion resistance in a severe corrosive environment, and surface appearance quality stably over a long period of time.
Means for solving the problems
The inventors of the present application have intensively studied and found that there is a correlation between the surface appearance quality of a cold-rolled steel strip and the iron ion concentration (hereinafter, also simply referred to as "Fe concentration") in a mixed acid when the cold-rolled steel strip is subjected to pickling with the mixed acid of the first stage. Specifically, as the Fe concentration in the mixed acid increases, the surface of the cold-rolled steel strip pickled with the mixed acid tends to change to reddish brown.
The inventors of the present application studied the cause and found that the pickling speed increases as Fe is gradually eluted from the cold-rolled steel sheet during the pickling process and the Fe concentration in the mixed acid increases. As a result, the generated reaction heat is equal to or higher than the cooling capacity of the mixed acid circulation equipment, and the liquid temperature of the mixed acid rises. Further, it has been found that when the cold-rolled steel strip is taken out from the pickling tank to the atmosphere, drying is promoted, and discoloration occurs by drying in a state where the mixed acid liquid remains. Therefore, from the viewpoint of ensuring good chemical conversion treatability and corrosion resistance after coating, although a certain amount of pickling weight reduction is ensured, it is necessary to appropriately control the pickling rate, that is, the liquid temperature of the mixed acid, depending on the Fe concentration in the mixed acid so as not to deteriorate the surface appearance quality.
The present invention has been completed based on the above-described findings, and the gist thereof is as follows.
(1) A method for producing a cold-rolled steel strip, characterized by comprising the steps of:
a step of continuously immersing the continuously annealed steel strip after the cold rolling in a mixed acid solution containing an oxidizing first acid and a non-oxidizing second acid to thereby carry out pickling, and
and then, a step of continuously immersing the steel strip in an acid solution containing a non-oxidizing third acid to perform a re-pickling process,
the concentration of the first acid in the mixed acid solution is changed to be lower and the concentration of the second acid is changed to be higher as the concentration of iron ions in the mixed acid solution increases.
(2) The method for producing a cold-rolled steel strip according to item (1) above, wherein the first acid is nitric acid.
(3) The method for producing a cold-rolled steel strip according to the item (1) or (2), wherein the second acid and/or the third acid is one or more acids selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid.
(4) The method for producing a cold-rolled steel strip according to item (1) above, wherein the first acid is nitric acid, and the second acid and the third acid are hydrochloric acid.
(5) The method for producing a cold-rolled steel strip according to item (4) above, wherein the nitric acid concentration is set to a range of greater than 110g/L and 188g/L or less, and the hydrochloric acid concentration is set to a range of greater than 4.5g/L and 12.5g/L or less in the mixed acid solution.
(6) The method for producing a cold-rolled steel strip according to any one of the above (1) to (5), wherein the steel strip is immersed in water after the pickling and before the re-pickling.
(7) The method for producing a cold-rolled steel strip according to any one of the above (1) to (6), wherein the total pickling weight loss in the pickling step and the re-pickling step is set to 8g/m2The above.
(8) The method for producing a cold-rolled steel strip according to any one of the above (1) to (7), wherein the steel strip contains 0.5 to 3.0 mass% of Si.
(9) A cold-rolled steel strip manufacturing apparatus is characterized by comprising:
a first raw liquid tank, a second raw liquid tank, and a third raw liquid tank for respectively storing a raw liquid of an oxidizing first acid, a non-oxidizing second acid, and a non-oxidizing third acid,
a first pipe, a second pipe, and a third pipe extending from the first raw liquid tank, the second raw liquid tank, and the third raw liquid tank, respectively,
a mixed acid solution circulation tank that connects the first pipe and the second pipe, mixes and stores the first acid supplied from the first raw liquid tank and the second acid supplied from the second raw liquid tank,
a first valve and a second valve provided in the first pipe and the second pipe, respectively, for adjusting a supply amount of the first acid from the first raw-liquid tank and a supply amount of the second acid from the second pipe, respectively,
an acid solution circulation tank connected to the third pipe and configured to contain the third acid supplied from the third raw liquid tank,
an acid mixing tank for containing a mixed acid solution containing the first acid and the second acid,
an acid tank for containing an acid solution containing the third acid,
at least 2 fourth pipes for connecting the circulation tank for the mixed acid liquid to the mixed acid tank and circulating the mixed acid liquid therebetween,
at least 2 fifth pipes for connecting the acid solution circulation tank to the acid tank and circulating the acid solution therebetween,
a strip passing facility for carrying the continuously annealed steel strip after cold rolling and continuously immersing the steel strip in the acid mixing tank and the acid tank in this order,
a concentration meter for measuring the concentration of iron ions in the mixed acid solution in the acid mixing tank, and
and a controller that controls the first valve and the second valve based on an output of the concentration meter such that the concentration of the first acid in the mixed acid liquid is changed to be lower and the concentration of the second acid in the mixed acid liquid is changed to be higher as the concentration of iron ions in the mixed acid liquid increases, the amount of the first acid supplied from the first raw-liquid tank is changed to be lower and the amount of the second acid supplied from the second raw-liquid tank is changed to be higher.
(10) The facility for producing a cold-rolled steel strip according to item (9) above, comprising a water tank that is located between the acid mixing tank and the acid tank and that contains water,
the strip passing device is configured to continuously dip the steel strip discharged from the acid mixing tank in the water tank and then continuously dip the steel strip in the acid tank.
(11) The apparatus for producing a cold-rolled steel strip according to the above (9) or (10), wherein the second acid and the third acid are the same acid, and the second raw-material tank and the third raw-material tank are the same tank.
Effects of the invention
The method and the facility for producing a cold-rolled steel strip according to the present invention can continuously produce a cold-rolled steel strip excellent in any of chemical conversion treatability, post-coating corrosion resistance in a severe corrosive environment, and surface appearance quality stably for a long period of time.
Drawings
Fig. 1 is a schematic view of a manufacturing facility 100 of a cold-rolled steel strip according to an embodiment of the present invention.
Fig. 2 shows SEM images of the coating surface (a), GDS analysis results (B), an image of a sample after the evaluation test of corrosion resistance after coating (C), and an image of the sample surface (D) in the comparative example.
Fig. 3 shows SEM images of the film surface (a), GDS analysis results (B), sample images after the evaluation test of corrosion resistance after coating (C), and sample surface images (D) in invention example 1.
Fig. 4 is an SEM image of the surface of the coating film in invention example 2, where (a) is a sample having an Fe concentration of 5g/L, (B) is a sample having an Fe concentration of 15g/L, and (C) is an image of a sample having an Fe concentration of 20 g/L.
Detailed Description
(method for producing Cold-rolled Steel strip)
A method for manufacturing a cold-rolled steel strip according to an embodiment of the present invention includes: a step of pickling the continuously annealed steel strip by continuously immersing the strip in a mixed acid solution containing an oxidizing first acid and a non-oxidizing second acid after the cold rolling, and a step of pickling the strip by continuously immersing the strip in an acid solution containing a non-oxidizing third acid.
(Pickling step)
In an annealing process using a continuous annealing furnace performed to impart desired structure, strength, and workability to a cold-rolled steel strip, generally, a non-oxidizing or reducing gas is used as an atmospheric gas, and the dew point is also strictly controlled. Therefore, in a general cold-rolled steel strip with a small amount of alloy added, oxidation of the surface of the steel strip is suppressed. However, even if the composition of the atmosphere gas and the dew point during annealing are strictly controlled in the cold-rolled steel strip containing 0.5 mass% or more of Si and Mn, it is inevitable that Si, Mn (which are more easily oxidized than Fe), and the like are oxidized to form Si oxide (SiO) on the surface of the steel strip2) Si-containing oxides such as Si-Mn based composite oxides. Since the Si-containing oxide is formed not only on the surface of the steel strip but also inside the base iron, the etching property of the surface of the steel strip in the chemical conversion treatment (zinc phosphate treatment) performed as the base treatment of the electrodeposition coating is impaired, and the formation of a sound chemical conversion coating film is adversely affectedAnd (6) sounding. In recent years, in order to reduce the amount of sludge generated during chemical conversion treatment and running cost, the temperature of the chemical conversion treatment liquid is lowered, and chemical conversion treatment is performed under conditions where the reactivity of the chemical conversion treatment liquid to the steel strip is remarkably low as compared with the conventional one. In this case, deterioration of the chemical conversion treatability is more remarkably exhibited.
Therefore, in the pickling step of the present embodiment, the cold-rolled steel strip is continuously immersed in a mixed acid solution containing an oxidizing first acid and a non-oxidizing second acid to remove the Si-containing oxide layer on the surface of the cold-rolled steel strip. The thickness of the Si-containing oxide layer varies depending on the composition of the steel strip and the annealing conditions (temperature, time, atmosphere), but is usually about 1 μm from the surface of the steel strip.
Nitric acid is an example of the oxidizing first acid. The reason why the first acid is required in the mixed acid solution is that although the Si — Mn-based composite oxide is easily dissolved in the acid among the Si-containing oxides, SiO is present2Since they are hardly soluble, it is necessary to remove the Si-containing oxide on the surface of the steel strip using an oxidizing acid such as nitric acid for each base iron.
The concentration of nitric acid in the mixed acid solution is preferably set to be in the range of more than 110g/L and 188g/L or less. This is because, when the concentration is 110g/L or less, the upper limit of the allowable Fe concentration in the mixed acid solution becomes low, and the time for which continuous pickling treatment can be performed without waste liquid treatment using the same mixed acid solution can be shortened, and when the concentration is more than 188g/L, it becomes difficult to dissolve the iron-based oxide in the subsequent re-pickling step. In addition, the higher the concentration of nitric acid, the more rapidly the Fe concentration in the mixed acid solution is increased, that is, the higher the allowable upper limit of the Fe concentration is reached. As a result, the time required for performing the continuous pickling treatment using the same mixed acid solution without performing the waste liquid treatment can be shortened. From the above viewpoint, the concentration of nitric acid is more preferably 140g/L or less, and still more preferably 130g/L or less.
The non-oxidizing second acid may be at least one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid, and hydrochloric acid, sulfuric acid, and hydrofluoric acid are particularly preferably used. The reason why such a non-oxidizing acid is used is to suppress the formation of iron-based oxides that precipitate on the surface of the steel strip as pickling with the oxidizing first acid.
The concentration of the second acid in the mixed acid solution is preferably set in a range of more than 4.5g/L and 12.5g/L or less. This is because, if the concentration is 4.5g/L or less, it is difficult to dissolve the iron-based oxide in the subsequent re-pickling step, and if the concentration is more than 12.5g/L, the pickling loss per unit time decreases, and SiO may remain on the surface layer of the steel strip2. More preferably, the concentration of the second acid in the mixed acid solution is 6.5g to 8.5 g/L.
The conditions that affect the amount of the Si-containing oxide are the composition of the steel strip and the annealing conditions, and the pickling time preferable for removing the Si-containing oxide is determined in consideration of these conditions. Therefore, the concentration of nitric acid, the passing speed, and the length of the pickling device may be set so that the above-described preferable pickling time can be ensured.
(Pickling step)
After the pickling step, Fe dissolved from the surface of the steel strip generates iron-based oxides, which precipitate on the surface of the steel strip to cover the surface of the steel strip, thereby degrading the chemical conversion treatability. Therefore, in the present embodiment, after the pickling step, the cold-rolled steel strip is continuously immersed in an acid solution containing a non-oxidizing third acid to remove the iron-based oxides. The "iron-based oxide" refers to an oxide mainly containing iron, in which the atomic concentration ratio of iron is 30% or more, among elements other than oxygen constituting the oxide. The iron-based oxide is present on the surface of the steel strip in a non-uniform thickness, and is different from a natural oxide film having a thickness of several nm, which is present uniformly in a layered form. As a result of observation with a Transmission Electron Microscope (TEM) and analysis of diffraction (diffraction pattern) by electron diffraction, the iron-based oxide formed on the surface of the cold-rolled steel strip was amorphous.
Examples of the non-oxidizing third acid include at least one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid, and hydrochloric acid, sulfuric acid, and hydrofluoric acid are particularly preferably used. Among these, hydrochloric acid is preferred because it is a volatile acid, and therefore it is difficult to leave residues such as sulfate radicals on the surface of the steel strip like sulfuric acid, and the effect of destroying iron-based oxides by chloride ions is large. In addition, an acid obtained by mixing hydrochloric acid and sulfuric acid may be used. The second acid used in the acid washing step and the third acid used in the present step may be the same type of acid or different types of acids. However, from the viewpoint of making it possible to share the production facilities, the same type of acid is preferable.
The concentration of the third acid in the acid solution is preferably set in a range of more than 4.5g/L and 12.5g/L or less. This is because, when the concentration is 4.5g/L or less, it is difficult to dissolve the iron-based oxide, and when the concentration is more than 12.5g/L, discoloration may occur due to the residual acid solution on the surface layer of the steel strip. More preferably, the concentration of the third acid in the acid solution is 6.5g to 8.5 g/L.
The preferable pickling time in the re-pickling step is determined based on the pickling reduction required to remove the iron-based oxide generated in the first-stage pickling, the pickling efficiency determined by the acid composition, and the pickling length. Usually, the acid temperature is about 30 to 60 ℃ and the pickling time is about 10 seconds.
After the continuous annealing, the cold-rolled steel strip pickled and re-pickled in the above-described manner is subjected to a usual treatment process such as temper rolling and straightening, thereby forming a cold-rolled steel sheet as a product sheet.
The total pickling weight loss in the pickling step and the re-pickling step is preferably set to 8g/m2The above. When the total weight loss of acid washing is 8g/m2In the above case, the Si-containing oxide and the iron-based oxide are less likely to remain on the surface of the steel strip, and therefore, higher chemical conversion treatability can be obtained.
(control of acid concentration in Mixed acid solution)
Here, the control of the acid concentration in the mixed acid, which is a characteristic configuration of the present invention, will be described. As described above, in a manufacturing facility capable of performing the above-described two-stage pickling, when the cold-rolled steel strip is continuously passed through the steel strip and the above-described two-stage pickling is continuously performed on the cold-rolled steel strip, a phenomenon occurs in which the surface of the cold-rolled steel strip after the pickling step in the first stage is discolored to reddish brown due to some deposits as time passes. Further, it is understood that this phenomenon is more likely to occur as the concentration of Fe in the mixed acid is higher. That is, it was found that the area ratio of discoloration of the surface of the cold-rolled steel strip immediately after the pickling with the mixed acid was increased as the Fe concentration in the mixed acid was increased.
As described above, this is because the temperature of the mixed acid solution increases as the Fe concentration in the mixed acid increases. Therefore, in the present embodiment, it is necessary to appropriately control the pickling rate, that is, the liquid temperature of the mixed acid, in accordance with the Fe concentration in the mixed acid. Specifically, as the Fe concentration in the mixed acid solution increases, the concentration of the first acid (for example, nitric acid) in the mixed acid solution is changed to be lower, and the concentration of the second acid (for example, hydrochloric acid) is changed to be higher.
In the present embodiment, it is preferable that the temperature of the mixed acid liquid is always maintained within the range of 45 to 55 ℃ by controlling the acid concentration as described above. This is because if the temperature is less than 45 ℃, the pickling loss per unit time is reduced, and SiO may remain on the surface layer of the steel strip2If the temperature is more than 55 ℃, discoloration of the steel strip surface begins to occur.
The method of changing the concentration of the first acid in the mixed acid solution to be lower and the concentration of the second acid to be higher as the Fe concentration in the mixed acid solution increases is not particularly limited, and for example, the following method can be employed.
The Fe concentration in the fresh mixed acid not used in the pickling of the steel strip is zero. The concentrations of the first acid and the second acid in the fresh mixed acid are set to be in the vicinity of the middle of the above-described preferable range. For example, the concentration of the first acid may be set to 132.5g/L and the concentration of the second acid may be set to 6.5 g/L.
Then, the Fe concentration in the mixed acid was measured over time. The Fe concentration may be measured constantly or intermittently for a fixed period.
Then, the Fe concentration is classified into a plurality of stages in advance, the set concentrations of the first and second acids are determined in advance for each stage, and the concentrations of the first and second acids are changed after the Fe concentration is shifted to the next stage. For example, in the stage where the Fe concentration in the mixed acid reaches 15g/L, the concentration of the first acid may be changed to 125.0g/L and the concentration of the second acid may be changed to 7.5 g/L. Further, in the case where the Fe concentration in the mixed acid reached 20g/L, the concentration of the first acid was set to 110.0g/L and the concentration of the second acid was set to 8.5 g/L.
Alternatively, the relational expression between the Fe concentration and the set concentrations of the first and second acids may be determined in advance, and the concentrations of the first and second acids may be changed at any time in accordance with the gradual increase in the Fe concentration in the mixed acid.
The timing of changing the acid concentration in the mixed acid, the value of the acid concentration in each stage, and the like are not particularly limited, and may be determined as appropriate in consideration of the composition of the steel strip, the annealing conditions, and the like.
In the present embodiment, even if the Fe concentration in the mixed acid is increased by controlling the acid concentration, the liquid temperature of the mixed acid can be maintained in a preferable range without increasing the pickling rate. As a result, it is possible to continuously produce a cold-rolled steel strip excellent in chemical conversion treatability, corrosion resistance after coating in a severe corrosive environment, and surface appearance quality for a long period of time.
(Cold-rolled Steel strip manufacturing facility)
Next, a manufacturing facility 100 of a cold-rolled steel strip according to an embodiment of the present invention, which can perform the above-described method of manufacturing a cold-rolled steel strip, will be described. The manufacturing apparatus 100 has, in order: a water tank 10 that stores water, an acid mixture tank 12 that stores an acid mixture (nitrohydrochloric acid) containing nitric acid as a first acid and hydrochloric acid as a second acid, a water tank 14 that stores water, an acid tank 16 that stores hydrochloric acid as a third acid, and a water tank 18 that stores water.
The strip passing facility includes rolls 11, 13, 15, 17, 19 immersed in the 5 tanks, respectively, and a plurality of rolls 20 positioned above the respective tanks, and is capable of continuously immersing the steel strip P in the order of the water tank 10, the mixed acid tank 12, the water tank 14, the acid tank 16, and the water tank 18 by carrying the continuously annealed steel strip P after cold rolling.
The manufacturing apparatus 100 includes a nitric acid raw liquid tank 20 for storing nitric acid as a first raw liquid tank, and a hydrochloric acid raw liquid tank 22 for storing hydrochloric acid as a second raw liquid tank and a third raw liquid tank. The first pipe 24 extends from the raw-solution tank for nitric acid 20, and the second pipe 26 and the third pipe 28 extend from the raw-solution tank for hydrochloric acid 22.
The mixed acid liquid circulation tank 30 is connected to the first pipe 24 and the second pipe 26, and mixes and stores the nitric acid supplied from the raw-acid-solution tank 20 and the hydrochloric acid supplied from the raw-acid-solution tank 22. The first pipe 24 is provided with a first valve 32 capable of adjusting the amount of nitric acid supplied from the raw-acid-for-nitric-acid tank 20. The second pipe 26 is provided with a second valve 34 capable of adjusting the supply amount of the hydrochloric acid from the raw-solution-for-hydrochloric-acid tank 22.
The acid solution circulation tank 40 is connected to the third pipe 28 and accommodates hydrochloric acid supplied from the hydrochloric acid raw liquid tank 22. A valve is also provided in the third pipe, and the supply amount of the hydrochloric acid from the hydrochloric acid raw liquid tank 22 can be adjusted.
The 2 fourth pipes 38 connect the circulation tank 30 for the mixed acid liquid and the mixed acid tank 12, and are pipes for circulating the mixed acid liquid therebetween. Valves are provided in each of the 2 fourth pipes 38, and the circulation amount of the mixed acid liquid can be adjusted by the valves. The circulation tank 30 for a mixed acid liquid is provided with a heat exchanger 36, and the temperature of the mixed acid liquid raised by the reaction heat can be lowered by the heat exchanger 36.
The 2 fifth pipes 42 connect the acid solution circulation tank 40 and the acid tank 16, and are pipes for circulating the hydrochloric acid solution therebetween. Valves are provided in each of the 2 fifth pipes 42, and the circulation amount of the hydrochloric acid solution can be adjusted by the valves. The acid solution circulation tank 40 is provided with a heat exchanger 44, and the heat exchanger 44 can suppress an increase in the temperature of the acid solution due to the reaction heat.
The manufacturing apparatus 100 has an Fe concentration meter 52 that measures the Fe concentration in the mixed acid liquid in the mixed acid tank 12. During the pickling, Fe is gradually eluted from the cold-rolled steel strip, and the Fe concentration in the mixed acid gradually increases. The increase in the Fe concentration in the mixed acid is detected as needed by the Fe concentration meter 52. As the Fe concentration meter 52, for example, an analyzer that irradiates the mixed acid liquid with near infrared rays at 1 minute intervals using near infrared spectroscopy and calculates the Fe concentration in the mixed acid liquid from the spectral change after the irradiation can be used. As shown in fig. 1, the mixed acid liquid supplied to the Fe concentration meter 52 may be sampled from the mixed acid tank 12, or may be sampled from the fourth pipe 38 leading from the mixed acid tank 12 to the circulation tank 30 for mixed acid liquid. The manufacturing facility 100 is configured to be able to sample the mixed acid from the circulation tank 30 and supply the sampled mixed acid to the Fe concentration meter 52. This is to measure the Fe concentration of the fresh mixed acid liquid when the mixed acid liquid in the circulation tank 30 is replaced.
The control unit 54 controls the first valve 32 and the second valve 34 based on the output of the Fe concentration meter 52. Specifically, as the Fe concentration in the mixed acid solution increases, the supply amount of nitric acid from the raw-acid tank 20 is changed to be smaller, and the supply amount of hydrochloric acid from the raw-acid tank 22 is changed to be larger, so that the nitric acid concentration in the mixed acid solution is changed to be lower, and the hydrochloric acid concentration is changed to be higher. The specific control method is as described above. The control unit 54 may be implemented by a Central Processing Unit (CPU) inside the computer.
In fig. 1, an example is shown in which the acid concentration in the mixed acid liquid is automatically controlled by the control unit 54, but the manufacturing method of the present invention is not limited to this, and the first valve 32 and the second valve 34 may be adjusted by an operator based on the measurement result obtained by the Fe concentration meter 52.
A waste liquid pipe 46 extends from the acid mixture circulation tank 30, a waste liquid pipe 48 extends from the acid mixture circulation tank 40, and waste liquid from each tank is sent to a waste liquid pit 50. The waste liquid conveyed to the waste liquid pit is subjected to pH treatment and N2Disposed of after treatment. The concentration of Fe in the nitric acid solution gradually increases, but the upper limit of the allowable Fe concentration is preferably set to a value of 25g/L or less. This is because if the Fe concentration in the nitrate acid solution is more than 25g/L, the reduction of the chemical conversion treatability cannot be suppressed even when the present invention is applied. Therefore, when the Fe concentration approaches 25g/L, nitric acid and hydrochloric acid are fed from the circulation tank 30 for mixed acid liquid to the waste liquid pit 50, and fresh nitric acid and hydrochloric acid are replenished from the raw liquid tanks 20 and 22. From the viewpoint of ensuring more excellent chemical conversion treatability, the nitrate acid solution allowsThe upper limit of the Fe concentration of (3) is more preferably set to a value of 15g/L or less. From the viewpoint of the efficiency of the operation, the lower limit of the allowable Fe concentration in the nitrate acid solution is preferably set to 10g/L or more. The waste hydrochloric acid solution from the acid solution circulation tank 40 is not particularly limited, and is used at a timing other than during the operation after a certain period of use.
In one embodiment, the amount A of nitric acid supplied from the raw-acid tank 20 to the mixed acid liquid circulation tank 30 may be set to 0.8 to 1.6m3The amount of hydrochloric acid B supplied from the hydrochloric acid raw liquid tank 22 to the acid mixture circulation tank 30 may be set to 0.1 to 0.3 m/hr3In terms of hours. A. B was changed at the timing of changing the concentrations of nitric acid and hydrochloric acid. The circulation amount C in the circulation tank 30 for the acid mixture liquid may be set to 25 to 90m3The amount of waste liquid D from the circulation tank 30 for acid mixture is set to 0 to 5 m/hr3The amount of hydrochloric acid E supplied from the hydrochloric acid raw liquid tank 22 to the acid liquid circulation tank 40 may be set to 1.0 to 2.0 m/hr3The circulation amount F in the acid solution circulation tank 40 may be set to 25 to 90 m/hr3The amount of waste liquid G from the acid liquid circulation tank 40 may be set to 0 to 5 m/hr3In terms of hours. C. D, E, F, G need not be particularly altered in operation.
Further, by providing the water tank 14 as in the present embodiment, the nitric acid and hydrochloric acid carried out of the acid mixing tank 12 by the steel strip P can be prevented from being mixed into the hydrochloric acid in the acid tank 16. Therefore, it is preferable to remove the iron-based oxide reliably by the re-pickling in the acid tank 16.
(composition of Cold-rolled Steel strip)
The composition of the cold-rolled steel strip to which the present invention is applied is not particularly limited, and preferably contains 0.5 to 3.0 mass% of Si. Si is an element effective for increasing the strength of steel without significantly losing workability, but is also an element that adversely affects chemical conversion treatability and corrosion resistance after coating. In order to increase the strength by adding Si, it is necessary to add 0.5 mass% or more. In addition, when Si is less than 0.5 mass%, the influence of deterioration of chemical conversion treatment conditions is small, and therefore the necessity of applying the present invention is low. On the other hand, if the Si content is more than 3.0 mass%, the steel is hardened, which adversely affects the rolling properties and the pass-through properties (manufacturability), and reduces the ductility of the steel strip itself. Therefore, Si is added in a range of 0.5 to 3.0 mass%. Preferably 0.8 to 2.5 mass%.
The composition range of the components other than Si, which are generally used in cold-rolled steel strips, is acceptable and is not particularly limited. Among them, when the present invention is applied to a high-strength cold-rolled steel sheet having a tensile strength TS of 590MPa or more used for automobile bodies and the like, it preferably has the following composition.
C: 0.01 to 0.30% by mass
C is an element effective for increasing the strength of steel, and is also an element effective for forming bainite, martensite, and retained austenite having a TRIP (Transformation Induced Plasticity) effect. The above-mentioned effects can be obtained by adding 0.01% by mass or more. Further, when the amount of C added is 0.30% by mass or less, the weldability is not greatly reduced. Therefore, C is preferably added in the range of 0.01 to 0.30 mass%. More preferably 0.10 to 0.20 mass%.
Mn: 1.0 to 7.5% by mass
Mn is an element having the action of strengthening the steel by solid solution strengthening, improving hardenability, and promoting the formation of retained austenite, bainite, and martensite. Such an effect can be exhibited by adding 1.0 mass% or more. On the other hand, excessive addition of Mn increases the cost of raw materials, and the allowable addition amount is 7.5 mass% or less. Therefore, Mn is preferably added in a range of 1.0 to 7.5 mass%. More preferably 2.0 to 5.0 mass%.
P: 0.05 mass% or less
P is an element having a strong solid solution strengthening ability without impairing drawability, and is an element effective for achieving high strength. In order to obtain the above effects, it is preferably contained in an amount of 0.005 mass% or more. On the other hand, since P is also an element that impairs spot weldability, the upper limit is preferably set to 0.05 mass%. More preferably 0.02 mass% or less.
S: 0.01% by mass or less
S is an impurity element inevitably mixed in the steel, and is a harmful component which is precipitated as MnS and lowers the stretch flangeability of the steel sheet. S is preferably limited to 0.01 mass% or less, more preferably 0.005 mass% or less, so as not to decrease stretch flangeability. More preferably 0.003 mass% or less. From the viewpoint of desulfurization cost, industrially, S is 0.0001 mass% or more.
Al: 0.06 mass% or less
Al is an element added as a deoxidizer in a steel making process, and is preferably contained in an amount of 0.01 mass% or more because Al is an element effective for separating a nonmetallic inclusion, which reduces stretch flangeability, as slag. However, since excessive addition increases the raw material cost, the upper limit of Al is preferably set to 0.06 mass%. More preferably in the range of 0.02 to 0.06 mass%.
The remainder of the cold-rolled steel strip to which the present invention is applied, excluding the above components, is Fe and inevitable impurities. The following components may be optionally contained therein.
For example, Ti, Nb, and V are elements useful for forming precipitates such as carbides and nitrides, increasing the strength of steel, suppressing ferrite growth, refining the structure, and improving formability (in particular, stretch flangeability). The above-mentioned effects can be obtained by adding 0.005% by mass or more to each element, and if it exceeds 0.3% by mass, the above-mentioned effects are saturated. Therefore, it is preferable to add 1 or 2 or more kinds of Ti, Nb and V in the range of 0.005 to 0.3 mass%, respectively. More preferably, the content is in the range of 0.005 to 0.2 mass%, respectively.
Mo and Cr are elements that improve hardenability of steel, promote formation of bainite and martensite, and contribute to high strength. The above-mentioned effects can be obtained by adding 0.005% by mass or more, respectively, and if it exceeds 0.3% by mass, the above-mentioned effects are saturated. Therefore, Mo and Cr are preferably added in the range of 0.005 to 0.3 mass%, respectively. More preferably, the content is in the range of 0.005 to 0.2% by mass, respectively.
Since B is an element effective for improving the hardenability of steel, 0.001 mass% or more and 0.006 mass% or less may be added. More preferably 0.002 mass% or less. Ni and Cu are effective elements for increasing the strength of steel, and may be added in a range of 0.001 mass% to 2.0 mass%, respectively.
N is an element that most deteriorates the aging resistance of steel, and particularly when N is more than 0.008 mass%, deterioration of aging resistance becomes remarkable. Therefore, the lower the N, the better, and preferably 0.008 mass% or less. More preferably, it is 0.006 mass% or less. Industrially, N is 0.001 mass% or more.
Ca and REM have an effect of spheroidizing the form of sulfides, and are effective elements for improving stretch flangeability. The above-mentioned effects can be obtained by adding 0.001 mass% or more, and if it exceeds 0.1 mass%, the cleanliness of the steel is lowered. Therefore, it is preferable that Ca and REM are added in the range of 0.001 to 0.1 mass%, respectively.
Examples
The operations described in the following invention examples and comparative examples were performed using the same manufacturing equipment as in fig. 1, except that the control unit was not provided. The cold-rolled steel strip having C in mass% was passed through the above-described manufacturing facility to be pickled and re-pickled: 0.125%, Si: 1.40%, Mn: 1.90%, P: 0.02%, S: 0.002%, and the balance of Fe and inevitable impurities, and was annealed in a continuous annealing furnace in a reducing atmosphere.
Comparative example
The concentration of nitric acid and the concentration of hydrochloric acid in the mixed acid were respectively 132.5g/L and 6.5g/L, respectively. The Fe concentration in the mixed acid at the start of the operation was 0 g/L. During the operation, the concentration of Fe was gradually increased, but the concentrations of nitric acid and hydrochloric acid in the mixed acid were not changed. The concentration of hydrochloric acid in the re-pickling step was 3 g/L. When the Fe concentration in the mixed acid solution reached 20g/L, pickling was performed, followed by re-pickling, and a sample was taken from the thus-obtained steel strip and subjected to the following evaluation. The total weight loss by pickling in the pickling step and the re-pickling step was 5.9g/m2。
(inventive example 1)
The concentration of nitric acid and the concentration of hydrochloric acid in the mixed acid at the start of the operation were 132.5g/L and 6.5g/L, respectively. The Fe concentration in the mixed acid at the start of the operation was 0 g/L. Since the Fe concentration gradually increased during the operation, the nitric acid concentration was changed to 125.0g/L and the hydrochloric acid concentration was changed to 7.5g/L at the stage when the Fe concentration in the mixed acid reached 15g/L, and the nitric acid concentration was changed to 110.0g/L and the hydrochloric acid concentration was changed to 8.5g/L at the stage when the Fe concentration in the mixed acid reached 20 g/L. The concentration of nitric acid and the concentration of hydrochloric acid in the mixed acid were changed by an operator. The concentration of hydrochloric acid in the re-pickling step was set to 6 g/L. When the Fe concentration in the mixed acid solution reached 20g/L, pickling was performed, followed by re-pickling, and a sample was taken from the thus-obtained steel strip and subjected to the following evaluation. The total weight loss by pickling in the pickling step and the re-pickling step was 21.3g/m2。
< evaluation of chemical conversion treatability >
The samples of comparative example and invention example 1 were subjected to chemical conversion treatment under the following conditions. The crystal grain size and coating quality of the phosphate coated chemical conversion crystal were measured. The crystal grain diameter which is a common control value is less than 5 μm, and the coating mass is 1.0-3.0 g/m3The preferable range is set. Further, the surface of the coating was observed by SEM at 1000 Xmagnification to confirm the presence or absence of the sites where no chemical conversion crystals were attached. In addition, the distribution of O, Si, Mn, and Fe in the depth direction of the surface layer of the sample was measured by GDS analysis, and the presence or absence of the Si peak of the surface layer was confirmed.
Chemical conversion treatment conditions:
the samples were degreased using a degreaser manufactured by Parkerizing Company, Japan: FC-E2011, surface conditioner: PL-X, and chemical conversion treatment agent: PALbonD PB-L3065, under the following conditions, the amount of film attached is 1.7-3.0 g/m2The chemical conversion treatment is carried out.
Degreasing: the treatment temperature is 40 ℃, and the treatment time is 120 seconds
Spraying degreasing and surface conditioning: pH9.5, room temperature and 20 s treatment time
A chemical conversion treatment process: the temperature of the chemical conversion treatment liquid was 35 ℃ and the treatment time was 120 seconds
The average crystal grain size was 6 μm in comparative example and 4 μm in inventive example 1. The comparative example was 0.9g/m in terms of coating quality3Inventive example 1 is 2.5g/m3. In addition, the SEM images of the film surface are shown in fig. 2(a) for a comparative example and fig. 3(a) for an invention example 1. In contrast to the comparative example in which the chemical conversion crystals were not adhered, the invention example 1 in which the chemical conversion crystals were uniform was observed. As a result of GDS analysis, the Si peak of the surface layer was detected as shown in fig. 2(B) in the comparative example, and was not detected as shown in fig. 3(B) in the invention example 1. From the above results, it is clear that comparative example is inferior in chemical conversion treatability, and invention example 1 is superior in chemical conversion treatability.
< evaluation of Corrosion resistance after coating >
The samples of comparative example and invention example 1 were subjected to chemical conversion treatment under the above conditions, and further, a plating coating material manufactured by japan Paint corporation: v-50, and applying a plating coating to the surface of the chemical conversion coating so that the thickness thereof becomes 25 μm. After a cross-cut mark having a length of 45mm was given to the surface of the test piece by a cutter, the test piece was subjected to a corrosion test in which 1 cycle of brine spray (5 mass% NaCl aqueous solution: 35 ℃, relative humidity: 98%) × 2 hours → dry (60 ℃, relative humidity: 30%) × 2 hours → wet (50 ℃, relative humidity: 95%) × 2 hours was repeated for 90 cycles, and after the corrosion test, washing with water and drying were performed, and then, a tape peeling test was performed on the cut mark portion. The maximum total peel width obtained by adding the left and right cut portions was measured. When the maximum peel total width was 6.0mm or less, the post-coating corrosion resistance was evaluated as good.
Fig. 2(C) shows an image of a test piece after the tape peeling test of the comparative example, and fig. 3(C) shows an image of a test piece after the tape peeling test of the invention example 1. In comparative example, the maximum total peel width was 7.9mm, and the corrosion resistance after coating was poor, whereas in invention example 1, the maximum total peel width was 5.6mm, and the corrosion resistance after coating was good.
< evaluation of surface appearance >
Fig. 2(D) shows an image of the sample surface of the comparative example, and fig. 3(D) shows an image of the sample surface of the invention example 1. As described above, the surface discoloration was reddish brown in the comparative example, but in the invention example 1, the discoloration did not occur, and the surface appearance was good.
(inventive example 2)
The Fe concentration in the mixed acid at the start of the operation was 5.0 g/L. The relationships between the nitric acid concentration and the hydrochloric acid concentration and the Fe concentration for ensuring the required reduction in acid washing are set in advance by the following relational expressions (1) and (2), respectively, and the nitric acid concentration at the start is 132.5g/L and the hydrochloric acid concentration is 5.5 g/L. The concentration of Fe in the mixed acid gradually increased during the operation, and the concentration of nitric acid and the concentration of hydrochloric acid were changed according to the formulas (1) and (2).
Concentration of nitric acid (g/L) · 140-1.5 × concentration of Fe (g/L) · (1)
Hydrochloric acid concentration (g/L) ═ 4.5+0.2 XFe concentration (g/L) · (2)
The concentration of hydrochloric acid in the re-pickling step was set to 8 g/L. When the Fe concentration in the mixed acid solution reached 5g/L, 15.0g/L, and 20g/L, pickling was performed, and then re-pickling was performed, and a sample was collected from the thus-obtained steel strip and subjected to the following evaluation. The total weight loss by pickling in the pickling step and the re-pickling step was 11.0g/m for the sample having an Fe concentration of 5g/L2The sample with Fe concentration of 15g/L was 12.0g/m2The sample with Fe concentration of 20g/L was 12.0g/m2。
The collected samples were evaluated for chemical conversion treatability, corrosion resistance after coating, and surface appearance in the same manner as in comparative example and invention example 1.
< evaluation result of chemical conversion treatability >
For the SEM image of the coating surface, a sample having an Fe concentration of 5g/L is shown in fig. 4(a), a sample having an Fe concentration of 15g/L is shown in fig. 4(B), and a sample having an Fe concentration of 20g/L is shown in fig. 4 (C). In either image, uniformity of the chemically converted crystals was observed. In any of the samples, no surface Si peak was detected in the GDS analysis. Therefore, it was found that the chemical conversion treatability of invention example 2 is also excellent.
< evaluation result of Corrosion resistance after coating >
For the maximum total width of peeling, 5.2mm was used for the sample with Fe concentration of 5g/L, 4.8mm was used for the sample with Fe concentration of 15g/L, and 5.6mm was used for the sample with Fe concentration of 20 g/L. Therefore, it is understood that invention example 2 has good corrosion resistance after coating, as in invention example 1.
< evaluation result of surface appearance >
The surfaces of the sample with the Fe concentration of 5g/L, the sample with the Fe concentration of 15g/L, and the sample with the Fe concentration of 20g/L were observed. No reddish-brown discoloration was found on the surface of any of the samples, giving a good surface appearance. In contrast, in the sample having an Fe concentration of 20g/L, coloration (stain) was slightly observed in a part of the surface, whereas in the sample having an Fe concentration of 5g/L and the sample having an Fe concentration of 15g/L, coloration was not observed, and a very beautiful surface appearance was exhibited. From this, it is found that the upper limit of the Fe concentration is preferably set to 15 g/L.
Industrial applicability
The method and the facility for producing a cold-rolled steel strip according to the present invention can continuously produce a cold-rolled steel strip excellent in any of chemical conversion treatability, post-coating corrosion resistance in a severe corrosive environment, and surface appearance quality stably for a long period of time. Therefore, the cold-rolled steel strip produced by the present invention can be preferably used for strength members of automobile bodies, parts for home electric appliances, building members, and the like.
Description of the reference numerals
100 cold-rolled steel strip manufacturing equipment
10. 14, 18 water tank
12 acid mixing tank (for nitric acid and hydrochloric acid)
16 acid tank (for hydrochloric acid)
11. 13, 15, 17, 19 and 20 rollers (plate passing equipment)
20 stock solution pot for nitric acid
22 stock solution tank for hydrochloric acid
24 first piping
26 second piping
28 third piping
30 circulation tank for acid mixing liquid
32 first valve
34 second valve
36 heat exchanger
38 fourth piping
40 circulation tank for acidizing fluid
42 fifth piping
44 heat exchanger
46. 48 piping for waste liquid
50 waste liquid pit
52Fe concentration meter
54 control part
Claims (12)
1. A method for producing a cold-rolled steel strip, characterized by comprising the steps of:
a step of pickling a continuously annealed steel strip by continuously immersing the strip in a mixed acid solution containing a first acid and a second acid after cold rolling, wherein the first acid is nitric acid, the second acid is one or more selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid, and
and then, a step of continuously immersing the steel strip in an acid solution containing a third acid, which is one or more selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid, to thereby perform re-pickling,
wherein,
in the mixed acid solution, the concentration of the first acid is set in a range of more than 110g/L and 188g/L or less, the concentration of the second acid is set in a range of more than 4.5g/L and 12.5g/L or less,
the concentration of the third acid in the acid solution is set in a range of more than 4.5g/L and 12.5g/L or less,
measuring the Fe concentration in the mixed acid solution over time,
changing the concentration of the first acid in the mixed acid solution to a lower concentration and changing the concentration of the second acid to a higher concentration as the concentration of Fe in the mixed acid solution increases, wherein the changing is performed in such a manner that the concentration of Fe in the mixed acid solution increases
(i) Classifying Fe into a plurality of stages in advance, determining set concentrations of the first acid and the second acid in advance for each stage, and changing the concentrations of the first acid and the second acid to the set concentrations or after the measured Fe concentration moves to the next stage
(ii) A relational expression between the Fe concentration and the set concentrations of the first acid and the second acid is determined in advance, and the concentrations of the first acid and the second acid are changed according to the relational expression at the time when the measured Fe concentration gradually increases.
2. The method for producing a cold-rolled steel strip according to claim 1, wherein the second acid and the third acid are hydrochloric acid.
3. The method of manufacturing a cold-rolled steel strip according to claim 1, wherein the steel strip is immersed in water after the pickling and before the re-pickling.
4. The method of manufacturing a cold-rolled steel strip according to claim 2, wherein the steel strip is immersed in water after the pickling and before the re-pickling.
5. The method for producing a cold-rolled steel strip according to claim 1, wherein the total pickling weight loss in the pickling step and the re-pickling step is set to 8g/m2The above.
6. The method for producing a cold-rolled steel strip according to claim 2, wherein the total pickling weight loss in the pickling step and the re-pickling step is set to 8g/m2The above.
7. The method for producing a cold-rolled steel strip according to claim 3, wherein the total pickling weight loss in the pickling step and the re-pickling step is set to 8g/m2The above.
8. The method for producing a cold-rolled steel strip according to claim 4, wherein the total pickling weight loss in the pickling step and the re-pickling step is set to 8g/m2The above.
9. The method for producing a cold-rolled steel strip as claimed in any one of claims 1 to 8, wherein the steel strip contains 0.5 to 3.0 mass% of Si.
10. A cold-rolled steel strip manufacturing apparatus is characterized by comprising:
a first raw liquid tank, a second raw liquid tank, and a third raw liquid tank that respectively contain raw liquids of a first acid, a second acid, and a third acid, wherein the first acid is nitric acid, the second acid is at least one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid, and the third acid is at least one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, formic acid, acetic acid, citric acid, hydrofluoric acid, and oxalic acid,
a first pipe, a second pipe, and a third pipe extending from the first raw liquid tank, the second raw liquid tank, and the third raw liquid tank, respectively,
a circulation tank for acid mixture liquid, which connects the first pipe and the second pipe, mixes and stores the first acid supplied from the first raw liquid tank and the second acid supplied from the second raw liquid tank,
a first valve and a second valve provided in the first pipe and the second pipe, respectively, for adjusting a supply amount of the first acid from the first raw-liquid tank and a supply amount of the second acid from the second pipe, respectively,
an acid solution circulation tank connected to the third pipe and configured to store the third acid supplied from the third raw liquid tank,
an acid mixing tank that contains a mixed acid solution containing the first acid and the second acid,
an acid tank for storing an acid solution containing the third acid,
at least 2 fourth pipes for connecting the circulation tank for the acid mixture liquid to the acid mixture tank and circulating the acid mixture liquid therebetween,
at least 2 fifth pipes for connecting the acid solution circulation tank to the acid tank and circulating the acid solution therebetween,
a strip passing facility for carrying the continuously annealed steel strip after cold rolling and continuously immersing the strip in the acid mixing tank and the acid tank in this order,
in the mixed acid solution, the concentration of the first acid is set in a range of more than 110g/L and 188g/L or less, the concentration of the second acid is set in a range of more than 4.5g/L and 12.5g/L or less,
the concentration of the third acid in the acid solution is set in a range of more than 4.5g/L and 12.5g/L or less,
the manufacturing apparatus further has:
a concentration meter for measuring the Fe concentration in the mixed acid solution in the acid mixing tank over time, and
a control unit that controls the first valve and the second valve based on an output of the concentration meter such that the higher the Fe concentration in the mixed acid liquid, the lower the supply amount of the first acid from the first raw-liquid tank and the higher the supply amount of the second acid from the second raw-liquid tank are, the lower the concentration of the first acid in the mixed acid liquid is, and the higher the concentration of the second acid is, the more the change is performed
(i) Classifying Fe into a plurality of stages in advance, determining set concentrations of the first acid and the second acid in advance for each stage, and changing the concentrations of the first acid and the second acid to the set concentrations or after the measured Fe concentration moves to the next stage
(ii) A relational expression between the Fe concentration and the set concentrations of the first acid and the second acid is determined in advance, and the concentrations of the first acid and the second acid are changed according to the relational expression at the time when the measured Fe concentration gradually increases.
11. The apparatus for manufacturing a cold-rolled steel strip according to claim 10, comprising a water tank containing water between the acid mixing tank and the acid tank,
the plate passing device is configured to continuously dip the steel strip in the acid tank after the steel strip coming out of the acid mixing tank is continuously dipped in the water tank.
12. The apparatus for manufacturing a cold-rolled steel strip according to claim 10 or 11, wherein the second acid and the third acid are the same acid, and the second raw-material tank and the third raw-material tank are the same tank.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015137186 | 2015-07-08 | ||
| JP2015-137186 | 2015-07-08 | ||
| PCT/JP2016/070755 WO2017007036A1 (en) | 2015-07-08 | 2016-07-07 | Process and equipment for producing cold-rolled steel strip |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107709620A CN107709620A (en) | 2018-02-16 |
| CN107709620B true CN107709620B (en) | 2020-04-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201680039032.XA Active CN107709620B (en) | 2015-07-08 | 2016-07-07 | Method and apparatus for manufacturing cold-rolled steel strip |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US20180298503A1 (en) |
| EP (1) | EP3321394B1 (en) |
| CN (1) | CN107709620B (en) |
| WO (1) | WO2017007036A1 (en) |
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| CN112226775A (en) * | 2020-09-16 | 2021-01-15 | 江苏华久辐条制造有限公司 | Cold-rolled steel pickling process |
| WO2022201686A1 (en) | 2021-03-26 | 2022-09-29 | Ｊｆｅスチール株式会社 | Method for producing annealed and pickled steel sheet |
| CN116917546A (en) * | 2021-03-26 | 2023-10-20 | 杰富意钢铁株式会社 | Method for producing annealed and pickled steel sheet |
| CN113737196B (en) * | 2021-09-09 | 2023-05-26 | 本钢板材股份有限公司 | Energy-saving strip steel pickling mechanism |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3021164B2 (en) * | 1992-02-14 | 2000-03-15 | 川崎製鉄株式会社 | Method for producing austenitic stainless steel with excellent surface gloss |
| JP3046132B2 (en) * | 1992-03-19 | 2000-05-29 | 日新製鋼株式会社 | Control method of nitric acid hydrofluoric acid bath for descaling stainless steel strip and its continuous descaling device |
| JP3078657B2 (en) * | 1992-07-03 | 2000-08-21 | 川崎製鉄株式会社 | Method for producing austenitic stainless steel with excellent surface abrasiveness |
| JP3021164U (en) * | 1995-07-31 | 1996-02-16 | 太陽誘電株式会社 | Optical information medium |
| JP3225880B2 (en) * | 1997-03-07 | 2001-11-05 | 住友金属工業株式会社 | Pickling method for stainless steel |
| JP5729211B2 (en) * | 2010-08-31 | 2015-06-03 | Ｊｆｅスチール株式会社 | Cold rolled steel sheet manufacturing method, cold rolled steel sheet and automobile member |
| JP5835558B2 (en) * | 2010-08-31 | 2015-12-24 | Ｊｆｅスチール株式会社 | Cold rolled steel sheet manufacturing method |
| JP5835545B2 (en) * | 2011-02-21 | 2015-12-24 | Ｊｆｅスチール株式会社 | Method for producing Si-containing hot-rolled steel sheet |
| JP5835547B2 (en) * | 2011-03-10 | 2015-12-24 | Ｊｆｅスチール株式会社 | Method for producing Si-containing cold-rolled steel sheet |
| JP5919920B2 (en) * | 2011-03-28 | 2016-05-18 | Ｊｆｅスチール株式会社 | Method and apparatus for producing Si-containing cold-rolled steel sheet |
-
2016
- 2016-07-07 US US15/737,904 patent/US20180298503A1/en not_active Abandoned
- 2016-07-07 EP EP16821503.6A patent/EP3321394B1/en active Active
- 2016-07-07 WO PCT/JP2016/070755 patent/WO2017007036A1/en active Application Filing
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| Publication number | Publication date |
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| EP3321394A1 (en) | 2018-05-16 |
| WO2017007036A1 (en) | 2017-01-12 |
| EP3321394A4 (en) | 2018-05-16 |
| CN107709620A (en) | 2018-02-16 |
| US20180298503A1 (en) | 2018-10-18 |
| EP3321394B1 (en) | 2019-12-11 |
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